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EP0144601B1 - Read head for magnetically sensing wiegand wires - Google Patents

Read head for magnetically sensing wiegand wires Download PDF

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Publication number
EP0144601B1
EP0144601B1 EP84111893A EP84111893A EP0144601B1 EP 0144601 B1 EP0144601 B1 EP 0144601B1 EP 84111893 A EP84111893 A EP 84111893A EP 84111893 A EP84111893 A EP 84111893A EP 0144601 B1 EP0144601 B1 EP 0144601B1
Authority
EP
European Patent Office
Prior art keywords
reading head
shaped core
working surface
flux
wiegand
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP84111893A
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German (de)
French (fr)
Other versions
EP0144601A1 (en
Inventor
Norbert Dr. Normann
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Doduco Solutions GmbH
Original Assignee
Doduco GmbH and Co KG Dr Eugen Duerrwaechter
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
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Publication of EP0144601A1 publication Critical patent/EP0144601A1/en
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Publication of EP0144601B1 publication Critical patent/EP0144601B1/en
Expired legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
    • F02P7/00—Arrangements of distributors, circuit-makers or -breakers, e.g. of distributor and circuit-breaker combinations or pick-up devices
    • F02P7/06—Arrangements of distributors, circuit-makers or -breakers, e.g. of distributor and circuit-breaker combinations or pick-up devices of circuit-makers or -breakers, or pick-up devices adapted to sense particular points of the timing cycle
    • F02P7/067—Electromagnetic pick-up devices, e.g. providing induced current in a coil
    • F02P7/0672—Electromagnetic pick-up devices, e.g. providing induced current in a coil using Wiegand effect
    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
    • G06K7/08—Methods or arrangements for sensing record carriers, e.g. for reading patterns by means detecting the change of an electrostatic or magnetic field, e.g. by detecting change of capacitance between electrodes
    • G06K7/082—Methods or arrangements for sensing record carriers, e.g. for reading patterns by means detecting the change of an electrostatic or magnetic field, e.g. by detecting change of capacitance between electrodes using inductive or magnetic sensors
    • G06K7/083—Methods or arrangements for sensing record carriers, e.g. for reading patterns by means detecting the change of an electrostatic or magnetic field, e.g. by detecting change of capacitance between electrodes using inductive or magnetic sensors inductive

Definitions

  • the invention relates to a reading head for magnetic scanning of Wiegand wires. It is based on a reading head with the features specified in the respective preamble of independent claims 1 and 2. Such a reading head is described in the older patent application DE-A-32 23 924, published on January 5, 1984. It is used to read information which is binary coded by means of Wiegand wires or the like. Magnetically bistable elements.
  • Wiegand wires are homogeneous in their composition, ferromagnetic wires (for example made of an alloy of iron and nickel, preferably 48% iron and 52% nickel, or of an alloy of iron and cobalt, or of an alloy of iron with cobalt and nickel, or from an alloy of cobalt with iron and vanadium, preferably 52% cobalt, 38% iron and 10% vanadium), which have a soft magnetic core and a hard magnetic jacket due to a special mechanical and thermal treatment, ie the jacket has a higher coercive force than the core.
  • Wiegand wires are typically 10 to 50 mm long, preferably 20 to 30 mm long.
  • This reversal is also known as a provision.
  • the direction of the external magnetic field is reversed again, the direction of magnetization of the core is reversed when a critical field strength of the external magnetic field (which is referred to as the ignition field strength) is exceeded, so that the core and the cladding are magnetized again in parallel.
  • This reversal of the direction of magnetization occurs very quickly and is accompanied by a correspondingly strong change in the magnetic force flow per unit of time (Wiegand effect).
  • This change in the power flow can induce a short and very high (depending on the number of turns and load resistance of the induction coil up to approx. 12 volts high) voltage pulse (Wiegand pulse) in an induction winding, which is referred to as a sensor winding.
  • a pulse is also generated in the sensor winding when the core is reset, but with a significantly lower amplitude and with the opposite sign as in the case of flipping from the anti-parallel to the parallel magnetization direction.
  • Wiegand wire lies in a magnetic field, the direction of which reverses from time to time and which is so strong that it can remagnetize the core first and then the cladding and bring it to magnetic saturation, then Wiegand pulses occur flipping the direction of magnetization of the soft magnetic core alternately with positive and negative polarity and one speaks of symmetrical excitation of the Wiegand wire. This requires field strengths of approx. - (80 to 120 A / cm) to + (80 to 120 A / cm).
  • the magnetization of the jacket is also abrupt and also leads to a pulse in the sensor winding, but the pulse is significantly smaller than the pulse induced when the core is folded over.
  • bistable magnetic elements are differently constructed bistable magnetic elements if they have two magnetically coupled areas of different hardness (coercive force) and can be used in a manner similar to Wiegand wires by induced, rapid folding over of the soft magnetic area to generate pulses.
  • a bistable magnetic switching core in the form of a wire which consists of a hard magnetic core (for example made of nickel-cobalt), an electrically conductive intermediate layer (for example made of copper) and deposited thereon consists of a soft magnetic layer (for example made of nickel-iron) deposited thereon.
  • Another variant additionally uses a core made of a magnetically non-conductive metallic inner conductor (for example made of beryllium copper), onto which the hard magnetic layer, then the intermediate layer and then the soft magnetic layer are deposited.
  • a bistable magnetic switching core generates fewer switching pulses than a Wiegand wire.
  • Another, two-layer, bistable magnetic element is from the magazine ELEKTRONIK 9.6.5.1983, p. 105 u. 106 known.
  • Wiegand wires information can be binary coded by providing two sequences of parallel Wiegand wires on a carrier, in such a way that the two sequences are offset in the longitudinal direction of the Wiegand wires, and that a Wiegand -Wire in one sequence corresponds to a gap in the other sequence of Wiegand wires. If you move the carrier with the two sequences of Wiegand wires past a reading head or, conversely, if you move the reading head past the carrier, each Wiegand wire moved past the reading head causes an electrical pulse in a sensor winding of the reading head. The read head differentiates between pulses from the first and second series of Wiegand wires and assigns them the values "0" and "1".
  • the read heads known for the stated purpose work with asymmetrical excitation of the Wiegand wires.
  • the reading head described in the aforementioned DE-A1-32 23 924 uses an E-shaped part as the core for the electrical sensor winding around the middle leg of which the sensor winding is placed.
  • the core is divided into two mutually parallel, soft magnetic, E-shaped partial cores by a non-magnetic intermediate layer.
  • the distance between the three legs of the E core and the length of the Wiegand wires in a carrier and the offset of the two sequences of Wiegand wires in this carrier are so coordinated in the prior art and also in the implementation of the present invention that Then, if the read head with the E core lying parallel to the Wiegand wires and the ends of the legs of the E core facing the Wiegand wires is moved along the support with the Wiegand wires, the two outer legs of the E core close to the ends of the Wiegand wires lying apart from one another lie from the two series of Wiegand wires, while the middle leg lies close to the intermediate middle ends of the Wiegand wires following from the two (see FIG.
  • the inclined position ensures that oppositely directed magnetic fields of different strengths exist on both sides of the E-core, of which the weaker for magnetic "reset” and the opposite for "ignition” (the ignition is occasionally used as a trigger for Wiegand Wires) of the Wiegand wires is used.
  • the two E-shaped partial cores are magnetized in opposite directions by the two inclined permanent magnets; they thus act as flux guide pieces, which concentrate the magnetic force flow especially at the tips of their three legs, but also bind them.
  • the known reading head has a further permanent magnet (also called a saturation magnet), which is spaced a few centimeters (typically 3 to 4 cm) is arranged away from the E core so that the fields of the saturation magnet and the remaining two magnets do not weaken each other too much.
  • a saturation magnet also called a saturation magnet
  • the arrangement of the magnets is chosen so that the magnetic field causing the reset of the Wiegand wires lies between the opposing magnetic fields for the saturation and the ignition of the Wiegand wires, is squeezed between the two, as it were, and the magnetic return of the Wiegand Wires at least the required field strength is accordingly only exceeded in a comparatively short area in the reading direction; an extension of this range would only be possible if the magnets were brought at a greater distance, and thus a longer overall length of the reading head was accepted.
  • the known reading head has the disadvantage that it has a large overall length of at least 5 cm in the reading direction (this is the direction in which the reading head is moved past the Wiegand wires or the Wiegand wires past the reading head), and that it is sensitive to changes in the distance between the Wiegand wires and the read head. Changes in distance of just a few tenths of a millimeter can lead to the failure of Wiegand pulses. This has the consequence that the well-known read head too is sensitive to tilting of the read head around an axis parallel to the Wiegand wires. In the known read head, the permissible tilt angle tolerance range is very small.
  • a large reading path is e.g. disadvantageous if cards coded with Wiegand wires have to be inserted into a slot of a reading device for reading, because then the cards must be at least the overall length of the reading head longer than the sequence of Wiegand wires on the card.
  • the aforementioned DE-A1-32 23 924 also describes a read head for only one row of Wiegand wires.
  • This read head differs from those for two lines of Wiegand wires i.w. only in that instead of an E-shaped core, a U-shaped core is used, the yoke of which carries the electrical winding and the tips of which reach the work surface and face the ends of the Wiegand wires being passed.
  • the disadvantages of the above-described read head with an E-shaped core also apply in the same way to the corresponding read heads with a U-shaped core.
  • the invention has for its object to provide a compact read head of the type mentioned, which is less sensitive to changes in its distance from Wiegand wires and to a tilt of the read head relative to the Wiegand wires.
  • the two permanent magnets, between which the E-shaped core lies can be used to generate such a high field strength at a location in front of the working surface of the reading head, without the aid of a separate saturation magnet, that it is sufficient to pull Wiegand wires saturate (i.e. at least 80 A / cm), and to generate an oppositely directed magnetic field at a nearby location in front of the working surface of the reading head, the field strength of which is sufficient to magnetically reset a previously magnetically saturated Wiegand wire, ie reached at least 16 A / cm.
  • Wiegand wires i.e. at least 80 A / cm
  • the working surface of the reading head is understood to mean that surface to which the tips of the three legs of the E-shaped core lead and to which the Wiegand wires are guided during the reading process.
  • the location at which the saturation field strength is reached and exceeded lies in front of the edges of the flux guide plates in the working surface of the reading head, which form strong local magnetic poles there, and so strong that the necessary saturation field strength is not only immediately in front of the working surface of the reading head, but also at some distance from it, so that the read head is not sensitive in this respect to small changes in distance from the Wiegand wires.
  • the necessary recovery field strength is achieved in a relatively extensive area in the reading direction and changes in the distance of the Wiegand wires from the working surface and tilting the Wiegand wires relative to the reading direction therefore have less of an effect on reading security than in the prior art, where the reset field strength is only achieved in a very short area in the reading direction between the opposing magnetic fields for the saturation and the ignition of the Wiegand wires.
  • the read head according to the invention is used. Reading process so guided or the Wiegand wires are guided during the reading process so that they first cross the weaker magnetic field responsible for the magnetic resetting of the Wiegand wires and then the edges of the flux guides in the working surface of the reading head and that of
  • Each Wiegand wire is therefore initially magnetically reset, then ignited with a steeply increasing field strength after passing the zero crossing of the magnetic field strength in the now oppositely directed magnetic field and driven further into the area of magnetic saturation. As a result of the saturation following the ignition or triggering of the Wiegand wire, it is ready for a further magnetic reset and ignition.
  • Wiegand wire has not been sufficiently saturated before a reset or has been exposed to an uncontrolled magnetic influence, which has nullified the effect of the previous saturation, you can fix it simply by changing the Wiegand wire after it did not ignite correctly during the first reading process, moved past the reading head again: now it will ignite safely, since it was saturated in any case during the first - incorrect - reading process.
  • Failed Wiegand pulses can be recognized within a coded pulse sequence by a test circuit without difficulty and if this occurs, the test circuit can emit a signal which prompts the read process to be repeated.
  • Suitable magnets for the invention are, owing to the high magnetic force fluxes that can be achieved with them, especially those made from rare earth alloys with cobalt, in particular from cobalt samarium.
  • the tips of the legs of the E-shaped core are located in the reading head according to the invention in the vicinity of the neutral zone of the magnetic field existing between the permanent magnets (the vicinity of the neutral zone is understood to mean the area around the spatial zero crossing of the field strength in which the magnetic field strength is still is substantially less than the field strength required to saturate the soft magnetic material from which the E-shaped core is made).
  • the Wiegand wires are fired at a relatively low field strength after they have passed through this neutral zone, that is to say also in the vicinity of the neutral zone and thus close to the ends of the legs of the E-shaped core, this ensures that the firing occurs of the Wiegand wire sudden change in a magnetic force flow directly affects the soft magnetic, E-shaped core, which couples the change in force flow further into the electrical winding (sensor winding), which is located on the middle leg of the E-shaped core.
  • the coupling of the change in force flow that occurs when a Wiegand wire is fired is, of course, best when the tips of the legs of the E-shaped core are located precisely at that location on the working surface of the reading head in front of which the Wiegand wire is fired.
  • the pulse amplitude that can be achieved in the sensor winding can be further increased significantly by an inclined position of the E-shaped core in the reading head, that this core is not only in the area of the working surface of the reading head, but overall in the vicinity of the neutral zone of the magnetic field, thus overall in the range of influence of the lowest possible magnetic field strength (claim 3).
  • Such an arrangement is advantageous because it avoids saturation of the E-shaped core by the magnet system and thus maintains the high permeability of the core.
  • the E-shaped core lies in the area of strong stray fields, which partially saturate it and thereby make it less responsive to further changes in the flow of force.
  • the core in the read head according to the invention does not require such a non-magnetic intermediate layer.
  • the neutral zone of the magnetic field runs through the entire E-core.
  • the use of flat components simplifies the construction of the reading head.
  • the magnets with their pole faces are expediently - at a right angle to - unlike in the prior art Reading direction oriented, and the E-shaped core accordingly has an angle of 90 ° to the reading direction.
  • the reading direction is perpendicular to the straight line connecting the tips of the legs of the e-core and parallel or tangential to the working surface of the reading head at this point.
  • the reading head shown in FIGS. 1-3 contains a soft-magnetic, E-shaped core 1 in a housing (not shown), around whose central leg 1c an electrical winding 2 (sensor winding) is placed, and two plate-shaped, that is to say short, permanent magnets 3 and 4 with relatively large pole faces.
  • the whole arrangement of core 1, winding 2 and magnet 3 is embedded in a plastic, in particular in a casting resin and thereby fixed in position.
  • the plastic itself is not shown, but the position of the working surface 6 of the reading head is indicated in FIG. 2 and in FIG. 3, which is formed by the surface of the plastic investment material and in which the tips 6a, 6b and 6c of the three legs 1a, 1b and 1c of the E-shaped core.
  • the two magnets 3 and 4 are the same size, the same strength and are arranged with their pole faces 3a and 3b or 4a and 4b at right angles to the reading direction 7.
  • the reading direction 7 is the direction in which the reading head is guided relative to the Wiegand wires 8 and 9, which are assumed to be at rest, during the reading process.
  • the connecting straight lines of the tips 6a, 6b and 6c of the three legs of the E-shaped core 1 are also arranged at right angles to the reading direction; However, as can best be seen from FIG. 2, the E core as a whole does not have a right angle with the reading direction 7, that is to say the two planes in which the two side faces of the E-shaped core 1 lie an angle other than 90 ° with the reading direction 7.
  • the tips 6a, 6b and 6c of the three legs of the E-shaped core 1 are chamfered in such a way that they lie in alignment with the work surface 5.
  • the two permanent magnets 3 and 4 are arranged at some distance below the work surface 5 and - measured in the direction transverse to the reading direction 7 - at some distance from the legs 1a and 1b of the E-shaped core 1.
  • the arrangement is such that the three legs 1a - 1c of the E-shaped core 1 cross the two magnets 3 and 4 approximately diagonally parallel to the working surface 5, but transversely to the reading direction 7 (see FIG. 2).
  • the two magnets 3 and 4 are oriented antiparallel relative to each other, and both carry a flux guide plate 13 or 14 on one of their pole faces 3a or 4b.
  • the flat flux guide plates 13 and 14 completely cover the respective pole surfaces 3a and 4b and lead to the edge of the magnets 3 and 4 closest to the working surface 5 to the working surface 5 of the reading head and, as seen in the plan view of the working surface, approach each other, see Fig. 1 - the two outer legs 1 and 1 b of the E-shaped core to a short distance. Measured in the reading direction 7, however, despite this approach, a considerable distance remains between the ends of the flow guide plates 13 and 14 lying in the working surface 5 and the tips 6a and 6b of the E-shaped core 1 (see FIG. 2).
  • the electrical winding 2 is oriented with its longitudinal axis perpendicular to the working surface 5 in the example shown and therefore includes an angle different from 0 with the central leg 1c of the E-shaped core, but such an orientation of the winding 2 is not mandatory.
  • the orientation of the electrical winding 2 is not essential to the invention, it could also be chosen differently.
  • the reading head shown in FIGS. 1 to 3 is used to read information which is coded in two rows of Wiegand wires, of which one Wiegand wire 8 or 9 is shown, for example.
  • the length of the Wiegand wires 8 and 9 and the position of the tips 6a, 6b and 6c of the E-shaped core 1 are coordinated with one another such that the Wiegand wires 8 of the one line have their ends over the tips 6a and 6c and Wiegand wires 9 of the other line are moved with their ends over the tips 6c and 6b of the E-shaped core 1 when the read head is guided in the reading direction transverse to the Wiegand wires 8 and 9 along the Wiegand wire parts.
  • a previously magnetically saturated Wiegand wire first reaches the relatively extensive magnetic field that is spanned between the two pole faces 3b and 4a and is magnetically reset by this.
  • the Wiegand wire 8 or 9 crosses a spatial zero crossing of the field strength and then reaches the area of the magnetic field, which is spanned between the pole faces 3a and 4b, which are covered with the flux guide plates 13 and 14, and which rises steeply beyond the spatial zero crossing of the field strength.
  • the Wiegand wire 8 or 9 Shortly after passing the zero crossing of the field strength, the Wiegand wire 8 or 9 is ignited and is driven to magnetic saturation when it reaches the area of the flux guide plates 13 and 14, between which there is a strong local magnetic field. As a result of this saturation following ignition, the Wiegand wire 8 or 9 is immediately ready for another reading process.
  • FIGS. 4 to 6 differs from that in FIGS. To 3 only in that instead of an E-shaped core 1, a U-shaped core 11 has been used, which has the required electrical winding on its yoke 12 2 wears.
  • a reading head is used to read the information contained in a single line of Wiegand wires 8.
  • the distance between the two legs 11 a and 11 b of the U-shaped core 11, the tips 16 a and 17 a are in turn in the working surface 6 of the reading head, is matched to the length of the Wiegand wires 8 that the ends of the Wiegand wires at Reading operation, when the reading head is guided at right angles to the Wiegand wires, be guided past the tips 16a and 16b of the core 11.

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Description

Die Erfindung betrifft einen Lesekopf zum magnetischen Abtasten von Wiegand-Drähten. Sie geht aus von einem Lesekopf mit den im jeweiligen Oberbegriff der unabhängigen Patentansprüche 1 und 2 angegebenen Merkmalen. Ein solcher Lesekopf ist in der älteren Patentanmeldung DE-A-32 23 924, veröffentlicht am 5. Januar 1984, beschrieben. Er dient zum Lesen von Informationen, welche mittels Wiegand-Drähten oder dergl. magnetisch bistabilen Elementen binär kodiert sind.The invention relates to a reading head for magnetic scanning of Wiegand wires. It is based on a reading head with the features specified in the respective preamble of independent claims 1 and 2. Such a reading head is described in the older patent application DE-A-32 23 924, published on January 5, 1984. It is used to read information which is binary coded by means of Wiegand wires or the like. Magnetically bistable elements.

Wiegand-Drähte sind in ihrer Zusammensetzung homogene, ferromagnetische Drähte (z.B. aus einer Legierung von Eisen und Nickel, vorzugsweise 48 % Eisen und 52 % Nickel, oder aus einer Legierung von Eisen und Kobalt, oder aus einer Legierung von Eisen mit Kobalt und Nickel, oder aus einer Legierung von Kobalt mit Eisen und Vanadium, vorzugsweise 52 % Kobalt, 38 % Eisen und 10 % Vanadium), die infolge einer besonderen mechanischen und thermischen Behandlung einen weichmagnetischen Kern und einen hartmagnetischen Mantel besitzen, d.h. der Mantel besitzt eine höhere Koerzitivkraft als der Kern. Wiegand-Drähte haben typisch eine Länge von 10 bis 50 mm, vorzugsweise von 20 bis 30 mm. Bringt man einen Wiegand-Draht, bei dem die Magnetisierungsrichtung des weichmagnetischen Kerns mit der Magnetisierungsrichtung des hartmagnetischen Mantels nach Sättigung des Wiegand-Drahtes in einem Magnetfeld mit einer Feldstärke von mindestens 80 A/cm, vorzugsweise mehr als 100 A/cm, übereinstimmt, in ein äußeres MagnétfeId, dessen Richtung mit der Richtung der Drahtachse übereinstimmt, der Magnetisierungsrichtung des Wiegand-Drahtes aber entgegengesetzt ist, dann wird bei Überschreiten einer Feldstärke von ca. 16 A/cm die Magnetisierungsrichtung des weichen Kerns des Wiegand-Drahtes umgekehrt.Wiegand wires are homogeneous in their composition, ferromagnetic wires (for example made of an alloy of iron and nickel, preferably 48% iron and 52% nickel, or of an alloy of iron and cobalt, or of an alloy of iron with cobalt and nickel, or from an alloy of cobalt with iron and vanadium, preferably 52% cobalt, 38% iron and 10% vanadium), which have a soft magnetic core and a hard magnetic jacket due to a special mechanical and thermal treatment, ie the jacket has a higher coercive force than the core. Wiegand wires are typically 10 to 50 mm long, preferably 20 to 30 mm long. Bring a Wiegand wire in which the magnetization direction of the soft magnetic core matches the magnetization direction of the hard magnetic sheath after saturation of the Wiegand wire in a magnetic field with a field strength of at least 80 A / cm, preferably more than 100 A / cm An external magnetic field, the direction of which coincides with the direction of the wire axis, but is opposite to the magnetization direction of the Wiegand wire, then the magnetization direction of the soft core of the Wiegand wire is reversed when a field strength of approx. 16 A / cm is exceeded.

Diese Umkehrung wird auch als Rückstellung bezeichnet. Bei erneuter Richtungsumkehr des äußeren Magnetfeldes kehrt sich die Magnetisierungsrichtung des Kerns bei Überschreiten einer kritischen Feldstärke des äußeren Magnetfeldes (welche man als Zündfeldstärke bezeichnet) erneut um, sodaß der Kern und der Mantel wieder parallel magnetisiert sind. Diese Umkehrung der Magnetisierungsrichtung erfolgt sehr rasch und geht mit einer entsprechend starken Änderung des magnetischen Kraftflusses pro Zeiteinheit einher (Wiegand-Effekt). Diese Änderung des Kraftflusses kann in einer Induktionswicklung, die als Sensorwicklung bezeichnet wird, einen kurzen und sehr hohen (ja nach Windungszahl und Belastungswiderstand der Induktionsspule bis zu ca. 12 Volt hohen) Spannungsimpuls induzieren (Wiegand-Impuls).This reversal is also known as a provision. When the direction of the external magnetic field is reversed again, the direction of magnetization of the core is reversed when a critical field strength of the external magnetic field (which is referred to as the ignition field strength) is exceeded, so that the core and the cladding are magnetized again in parallel. This reversal of the direction of magnetization occurs very quickly and is accompanied by a correspondingly strong change in the magnetic force flow per unit of time (Wiegand effect). This change in the power flow can induce a short and very high (depending on the number of turns and load resistance of the induction coil up to approx. 12 volts high) voltage pulse (Wiegand pulse) in an induction winding, which is referred to as a sensor winding.

Auch beim Zurückstellen des Kerns wird in der Sensorwicklung ein Impuls erzeugt, allerdings mit wesentlich geringerer Amplitude und mit umgekehrtem Vorzeichen wie im Falle des Umklappens von der antiparallelen in die parallele Magnetisierungsrichtung. Liegt der Wiegand-Draht in einem Magnetfeld, dessen Richtung sich von Zeit zu Zeit umkehrt und welches so stark ist, daß es zuerst den Kern und danach auch den Mantel ummagnetisieren und jeweils bis in die magnetische Sättigung bringen kann, so treten Wiegand-Impulse infolge des Umklappens der Magnetisierungsrichtung des weichmagnetischen Kerns abwechselnd mit positiver und negativer Polarität auf und man spricht von symmetrischer Erregung des Wiegand-Drahtes. Dazu benötigt man Feldstärken von ca. -(80 bis 120 A/cm) bis + (80 bis 120 A/cm). Das Ummagnetisieren des Mantels erfolgt ebenfalls sprunghaft und führt ebenfalls zu einem Impuls in der Sensorwicklung, jedoch ist der Impuls wesentlich kleiner als der beim Umklappen des Kerns induzierte Impuls.A pulse is also generated in the sensor winding when the core is reset, but with a significantly lower amplitude and with the opposite sign as in the case of flipping from the anti-parallel to the parallel magnetization direction. If the Wiegand wire lies in a magnetic field, the direction of which reverses from time to time and which is so strong that it can remagnetize the core first and then the cladding and bring it to magnetic saturation, then Wiegand pulses occur flipping the direction of magnetization of the soft magnetic core alternately with positive and negative polarity and one speaks of symmetrical excitation of the Wiegand wire. This requires field strengths of approx. - (80 to 120 A / cm) to + (80 to 120 A / cm). The magnetization of the jacket is also abrupt and also leads to a pulse in the sensor winding, but the pulse is significantly smaller than the pulse induced when the core is folded over.

Wählt man jedoch als äußeres Magnetfeld ein solches welches nur in der Lage ist, den weichen Kern, nicht aber den harten Mantel in seiner Magnetisierungsrichtung umzukehren, dann treten die hohen Wiegand-Impulse nur mit gleichbleibender Polarität auf und man spricht von asymmetrischer Erregung des Wiegand-Drahtes. Dazu benötigt man in der einen Richtung eine Feldstärke von wenigstens 16 A/cm (für die Rückstellung des Wiegand-Drahtes) und in der umgekehrten Richtung eine Feldstärke von ca. 80 bis 120 A/cm.However, if you choose an external magnetic field that is only able to reverse the soft core, but not the hard cladding in its magnetization direction, then the high Wiegand pulses only occur with constant polarity and one speaks of asymmetrical excitation of the Wiegand Wire. This requires a field strength of at least 16 A / cm in one direction (for resetting the Wiegand wire) and a field strength of approx. 80 to 120 A / cm in the opposite direction.

Charakteristisch für den Wiegand-Effekt ist, daß die durch ihn erzeugten Impulse in Amplitude und Breite weitgehend unabhängig sind won der Änderungsgeschwindigkeit des äußeren Magnetfeldes und ein hohes Signal-zu-Rausch-Verhältnis aufweisen.It is characteristic of the Wiegand effect that the pulses and amplitude generated by it are largely independent, which means that the rate of change of the external magnetic field and a high signal-to-noise ratio.

Für die Erfindung geeignet sind auch anders aufgebaute bistabile magnetischen Elemente, wenn diese zwei magnetisch miteinander gekoppelte Bereiche von unterschiedlicher Härte (Koerzitivkraft) besitzen und in ähnlicher Weise wie Wiegand-Drähte durch induziertes, rasch erfolgendes Umklappen des weichmagnetischen Bereichs zur Impulserzeugung verwendet werden können. So ist zum Beispiel aus der DE-A1-25 14 131 ein bistabiler magnetischer Schaltkern in Gestalt eines Drahtes bekannt, der aus einem hartmagnetischen Kern (z.B. aus Nickel-Kobalt), aus einer darauf abgeschiedenen, elektrisch leitenden Zwischenschicht (z.B. aus Kupfer) und aus einer hierauf abgeschiedenen weichmagnetischen Schicht (z.B. aus Nickel-Eisen) besteht. Eine andere Variante verwendet zusätzlich einen Kern aus einem magnetisch nicht leitenden metallischen Innenleiter (z.B. aus Beryllium-Kupfer), auf den dann die hartmagnetische Schicht, darauf die Zwischenschicht und darauf die weichmagnetische Schicht abgeschieden werden. Dieser bekannte bistabile magnetische Schaltkern erzeugt allerdings geringere Schaltimpulse als ein Wiegand-Draht.Also suitable for the invention are differently constructed bistable magnetic elements if they have two magnetically coupled areas of different hardness (coercive force) and can be used in a manner similar to Wiegand wires by induced, rapid folding over of the soft magnetic area to generate pulses. For example, from DE-A1-25 14 131 a bistable magnetic switching core in the form of a wire is known, which consists of a hard magnetic core (for example made of nickel-cobalt), an electrically conductive intermediate layer (for example made of copper) and deposited thereon consists of a soft magnetic layer (for example made of nickel-iron) deposited thereon. Another variant additionally uses a core made of a magnetically non-conductive metallic inner conductor (for example made of beryllium copper), onto which the hard magnetic layer, then the intermediate layer and then the soft magnetic layer are deposited. However, this known bistable magnetic switching core generates fewer switching pulses than a Wiegand wire.

Ein weiteres, ebenfalls zweischichtig aufgebautes, bistabiles magnetisches Element ist aus der Zeitschrift ELEKTRONIK 9,6.5.1983, S. 105 u. 106 bekannt.Another, two-layer, bistable magnetic element is from the magazine ELEKTRONIK 9.6.5.1983, p. 105 u. 106 known.

Mit Wiegand-Drähten lassen sich Informationen dadurch binär kodieren, daß man zwei Folgen von untereinander parallelen Wiegand-Drähten auf einem Träger vorsieht, und zwar in der Weise, daß die beiden Folgen in Längsrichtung der Wiegand-Drähte gegeneinander versetzt sind, und daß einem Wiegand-Draht in der einen Folge eine Lücke in der anderen Folge von Wiegand-Drähten entspricht. Bewegt man den Träger mit den beiden Folgen von Wiegand-Drähten an einem Lesekopf vorbei bzw. bewegt man umgekehrt den Lesekopf an dem Träger vorbei, dann bewirkt jeder am Lesekopf vorbeibewegte Wiegand-Draht in einer Sensorwicklung des Lesekopfes einen elektrischen Impuls. Der Lesekopf unterscheidet dabei zwischen Impulsen aus der ersten und aus der zweiten Folge von Wiegand-Drähten und ordnet diesen die Werte "0" bzw. "1" zu.With Wiegand wires, information can be binary coded by providing two sequences of parallel Wiegand wires on a carrier, in such a way that the two sequences are offset in the longitudinal direction of the Wiegand wires, and that a Wiegand -Wire in one sequence corresponds to a gap in the other sequence of Wiegand wires. If you move the carrier with the two sequences of Wiegand wires past a reading head or, conversely, if you move the reading head past the carrier, each Wiegand wire moved past the reading head causes an electrical pulse in a sensor winding of the reading head. The read head differentiates between pulses from the first and second series of Wiegand wires and assigns them the values "0" and "1".

Die für den angegebenen Zweck bekannten Leseköpfe arbeiten mit asymmetrischer Erregung der Wiegand-Drahte. Der in der eingangs erwähnten DE-A1-32 23 924 beschriebene Lesekopf verwendet als Kern für die elektrische Sensorwicklung ein E-förmiges Teil um dessen mittleren Schenkel die Sensorwicklung herumgelegt ist. Der Kern ist durch eine nichtmagnetische Zwischenschicht in zwei zueinander parallele, weichmagnetische, E-förmige Teilkerne unterteilt.The read heads known for the stated purpose work with asymmetrical excitation of the Wiegand wires. The reading head described in the aforementioned DE-A1-32 23 924 uses an E-shaped part as the core for the electrical sensor winding around the middle leg of which the sensor winding is placed. The core is divided into two mutually parallel, soft magnetic, E-shaped partial cores by a non-magnetic intermediate layer.

Der Abstand der drei Schenkel des E-Kerns voneinander und die Länge der Wiegand-Drähte in einem Träger sowie der Versatz der zwei Folgen von Wiegand-Drähten in diesem Träger werden beim Stand der Technik und auch bei Ausführung der vorliegenden Erfindung so aufeinander abgestimmt, daß dann, wenn man den Lesekopf mit zu den Wiegand-Drähten parallel liegendem E-Kern und den Wiegand- Drähten zugewandten Enden der Schenkel des E-Kerns am Träger mit den Wiegand-Drähten entlang bewegt, die beiden äußeren Schenkel das E-Kerns nahe den voneinander entfernt liegenden Enden der Wiegand-Drähte aus den beiden Folgen von Wiegand-Drähten liegen, während der mittlere Schenkel nahe den dazwischen liegenden, mittleren Enden der Wiegand-Drähte aus den beiden folgen liegt (vergl. Fig. 1)- Dies hat zur Folge, daß die mit der Ummagnetisierung eines Wiegand-Drahtes einhergehende kurzzeitige Änderung des magentischen Kraftlusses zu Impulsen unterschiedlicher Polarität in der Sensorwicklung führt, jenachdem, welcher der beiden Folgen von Wiegand-Drähten der den Impuls auslösende Wiegand-Draht angehört.The distance between the three legs of the E core and the length of the Wiegand wires in a carrier and the offset of the two sequences of Wiegand wires in this carrier are so coordinated in the prior art and also in the implementation of the present invention that Then, if the read head with the E core lying parallel to the Wiegand wires and the ends of the legs of the E core facing the Wiegand wires is moved along the support with the Wiegand wires, the two outer legs of the E core close to the ends of the Wiegand wires lying apart from one another lie from the two series of Wiegand wires, while the middle leg lies close to the intermediate middle ends of the Wiegand wires following from the two (see FIG. 1) - this has the consequence that the short-term change in the flux of magnetic force associated with the remagnetization of a Wiegand wire leads to pulses of different polarity in the sensor winding, which of the two series of Wiegand wires the Wiegand wire triggering the pulse belongs to.

Die zur Impulsauslösung erforderliche asymmetrische Erregung er Wiegand-Drähte erfolgt bei dem bekannten Lesekopf durch zwei kurze Dauermagnete, welche "oberhalb" des oberen Schenkels und "unterhalb" des unteren Schenkels des E-Kerns angeordnet sind und deren auf den Polflächen stehenden Normalen mit jener Ebene, in welcher die drei Schenl und der Rücken des E-Kerns liegen, einen zwischen 60° und 80° betragenden Winkel einschließen und parallel zu den Endflächen der drei Schenkel des E-Kerns liegen. (Die Bezeichnungen "oberhalb"und "unterhalb" beziehen sich auf eine Orientierung der Wiegand-Drähte in vertikaler Richtung). Durch die Schrägstellung wird erreicht, daß auf den beiden Seiten des E-Kerns entgegengesetzt gerichtete Magnetfelder unterschiedlicher Stärke bestehen, von denen das schwächere zur magnetischen "Rückstellung" und das entgegengesetzt gerichtete zur "Zündung" (die Zündung wird gelegentlich auch als Triggerung der Wiegand-Drähte bezeichnet) der Wiegand-Drähte ausgenutzt wird. Durch die beiden schräggestellten Dauermagnete werden die beiden E-förmigen Teilkerne in entgegengesetzten Richtungen magnetisiert; sie wirken somit als Flußleitstücke, welche den magnetischen Kraftfluß besonders an den Spitzen ihrer drei Schenkel konzentrieren, aber auch binden. Für die zusätzlich erforderliche Sättigung der Wiegand-Drähte in einem Magnetfeld, dessen Richtung mit dem zur Zündung erforderlichen Magnetfeld übereinstimmt, besitzt der bekannte Lesekopf einen weiteren Dauermagneten (auch als Sättigungsmagnet bezeichnet), welcher im Abstand von einigen Zentimetern (typisch 3 bis 4 cm) vom E-Kern entfernt angeordnet ist, damit die Felder des Sättigungsmagneten und der übrigen zwei Magnete einander nicht zu stark schwächen. Die Anordnung der Magnete ist dabei so gewählt, daß das die Rückstellung der Wiegand-Drähte bewirkende Magnetfeld zwischen den ihm entgegengesetzt gerichteten Magnetfeldern für die Sättigung und die Zündung der Wiegand-Drähte liegt, zwischen beiden gleichsam eingezwängt ist und die für eine magnetische Rückstellung der Wiegand-Drähte mindestens benötigte Feldstärke demgemäß nur in einem in Leserichtung vergleichsweise kurz bemessenen Bereich überschritten wird; eine Verlängerung dieses Bereichs wäre nur möglich, wenn man die Magnete auf größeren Abstand brächte, und damit eine größere Baulänge des Lesekopfes in Kauf nähme.The asymmetrical excitation of Wiegand wires required for triggering the pulse takes place in the known reading head by means of two short permanent magnets which are arranged "above" the upper leg and "below" the lower leg of the E-core and their normals on the pole faces with that plane , in which the three legs and the back of the E-core lie, enclose an angle between 60 ° and 80 ° and lie parallel to the end faces of the three legs of the E-core. (The terms "above" and "below" refer to an orientation of the Wiegand wires in the vertical direction). The inclined position ensures that oppositely directed magnetic fields of different strengths exist on both sides of the E-core, of which the weaker for magnetic "reset" and the opposite for "ignition" (the ignition is occasionally used as a trigger for Wiegand Wires) of the Wiegand wires is used. The two E-shaped partial cores are magnetized in opposite directions by the two inclined permanent magnets; they thus act as flux guide pieces, which concentrate the magnetic force flow especially at the tips of their three legs, but also bind them. For the additionally required saturation of the Wiegand wires in a magnetic field, the direction of which coincides with the magnetic field required for the ignition, the known reading head has a further permanent magnet (also called a saturation magnet), which is spaced a few centimeters (typically 3 to 4 cm) is arranged away from the E core so that the fields of the saturation magnet and the remaining two magnets do not weaken each other too much. The arrangement of the magnets is chosen so that the magnetic field causing the reset of the Wiegand wires lies between the opposing magnetic fields for the saturation and the ignition of the Wiegand wires, is squeezed between the two, as it were, and the magnetic return of the Wiegand Wires at least the required field strength is accordingly only exceeded in a comparatively short area in the reading direction; an extension of this range would only be possible if the magnets were brought at a greater distance, and thus a longer overall length of the reading head was accepted.

Bei dem bekannten Lesekopf ist aber gerade nachteilig, daß er in Leserichtung (das ist die Richtung, in welcher der Lesekopf an den Wiegand-Drähten oder die Wiegand-Drähte am Lesekopf vorbeibewegt werden) ohnehin eine große Baulänge von mindestens 5 cm aufweist, und daß er empfindlich gegen Änderungen des Abstands zwischen den-Wiegand-Drähten und dem Lesekopf ist. Bereits Abstandsänderungen um wenige Zehntel Millimeter können zum Ausfall von Wiegand-Impulsen führen. Dies hat zur Folge, daß der bekannte Lesekopf auch empfindlich ist gegen ein Verkippen des Lesekopfes um eine zu den Wiegand-Drähten parallele Achse. Bei dem bekannten Lesekopf ist der zulässige Kippwinkeltoleranzbereich sehr klein.However, the known reading head has the disadvantage that it has a large overall length of at least 5 cm in the reading direction (this is the direction in which the reading head is moved past the Wiegand wires or the Wiegand wires past the reading head), and that it is sensitive to changes in the distance between the Wiegand wires and the read head. Changes in distance of just a few tenths of a millimeter can lead to the failure of Wiegand pulses. This has the consequence that the well-known read head too is sensitive to tilting of the read head around an axis parallel to the Wiegand wires. In the known read head, the permissible tilt angle tolerance range is very small.

Bereits eine geringe Verkippung des Lesekopfes kann zum Ausfall von Wiegand-Impulsen führen. Diese Anfälligkeit des bekannten Lesekopfes gegen Abstandänderungen und Verkippung bezüglich der Wiegand-Drähte steht seiner Verwendung als handgeführter Lesekopf entgegen, und die große Baulänge bedingt einen entsprechend langen Leseweg. Ein großer Leseweg ist z.B. nachteilig, wenn mit Wiegand-Drähten kodierte Karten zum Lesen in einen Schlitz eines Lesegerätes gesteckt werden müssen, denn dann müssen die Karten wenigstens um die Baulänge des Lesekopfes länger sein als die auf der Karte befindliche Folge von Wieganddrähten.Even a slight tilt of the read head can lead to failure of Wiegand pulses. This susceptibility of the known reading head to changes in distance and tilting with respect to the Wiegand wires is contrary to its use as a hand-guided reading head, and the large overall length means that the reading path is correspondingly long. A large reading path is e.g. disadvantageous if cards coded with Wiegand wires have to be inserted into a slot of a reading device for reading, because then the cards must be at least the overall length of the reading head longer than the sequence of Wiegand wires on the card.

Die eingangs genannte DE-A1-32 23 924 beschreibt ferner einen Lesekopf für nur eine Zeile von Wiegand-Drähten. Dieser Lesekopf unterscheidet sich von jenen für zwei Zeilen von Wiegand-Drähten i.w. nur darin, daß anstelle eines E-förmigen Kerns ein U-förmiger Kern verwendet wird, dessen Joch die elektrische Wicklung trägt und dessen an die Arbeitsfläche reichenden Spitzen den Enden der vorbeigeführten Wiegand-Drähte zugewandt sind. Die Nachteile des vorbeschriebenen Lesekopfes mit E-förmigem Kern gelten in gleicher Weise auch für die entsprechenden Leseköpfe mit U-förmigem Kern.The aforementioned DE-A1-32 23 924 also describes a read head for only one row of Wiegand wires. This read head differs from those for two lines of Wiegand wires i.w. only in that instead of an E-shaped core, a U-shaped core is used, the yoke of which carries the electrical winding and the tips of which reach the work surface and face the ends of the Wiegand wires being passed. The disadvantages of the above-described read head with an E-shaped core also apply in the same way to the corresponding read heads with a U-shaped core.

Der Erfindung liegt die Aufgabe zugrunde, einen kompakten Lesekopf der eingangs genannten Art zu schaffen, der weniger empfindlich auf Änderungen seines Abstands von Wiegand-Drähten und auf eine Verkippung des Lesekopfes relativ zu den Wiegand-Drähten reagiert.The invention has for its object to provide a compact read head of the type mentioned, which is less sensitive to changes in its distance from Wiegand wires and to a tilt of the read head relative to the Wiegand wires.

Diese Aufgabe wird gelöst durch einen Lesekopf mit den im Patentanspruch 1 angegebenen Merkmalen für das Abtasten von zwei Zeilen von Wiegand-Drähten und durch einen Lesekopf mit den im Patentanspruch 2 angegebenen Merkmalen für das Abtasten von nur einer Zeile von Wiegand-Drähten. Weiterbildungen der Erfindung sind Gegenstand der Unteransprüche.This object is achieved by a reading head with the features specified in claim 1 for scanning two lines of Wiegand wires and by a reading head with the features specified in claim 2 for scanning only one line of Wiegand wires. Developments of the invention are the subject of the dependent claims.

Die Vorteile der Erfindung werden nachstehend am Beispiel des Lesekopfes mit E-förmigem Kern erläutert. Sie gelten in gleicher Weise für einen entsprechenden Lesekopf mit U-förmigem Kern.The advantages of the invention are explained below using the example of the reading head with an E-shaped core. They apply in the same way to a corresponding read head with a U-shaped core.

Durch den neuartigen Lesekopfaufbau gelingt es, allein mit den beiden Dauermagneten, zwischen welchen der E-förmige Kern liegt, ohne Zuhilfenahme eines gesonderten Sättigungsmagneten an einem Ort vor der Arbeitsfläche des Lesekopfes eine so hohe Feldstärke zu erzeugen, welche ausreicht, um Wiegand-Drähte zu sättigen (also mindestens 80 A/cm), und an einem nahe benachbarten Ort vor der Arbeitsfläche des Lesekopfes ein entgegengesetzt gerichtetes Magnetfeld zu erzeugen, dessen Feldstärke ausreicht, einen zuvor magnetisch gesättigten Wiegand-Draht magnetisch zurückzustellen, d.h. mindestens den Wert 16 A/cm erreicht. Diese beiden Orte werden beim Lesevorgang von den Wiegand-Drähten passiert. Unter der Arbeitsfläche des Lesekopfes wird jene Oberfläche verstanden, zu welcher die Spitzen der drei Schenkel des E-förmigen Kerns führen und an welcher die Wiegand-Drähte beim Lesevorgang entlanggeführt werden. Der Ort, an welchem die Sättigungsfeldstärke erreicht und überschritten wird, liegt vor den in der Arbeitsfläche des Lesekopfes liegenden Rändern der Flußleitbleche, welche dort starke lokale Magnetpole bilden, und zwar so stark, daß die nötige Sättigungsfeldstärke nicht nur unmittelbar vor der Arbeitsfläche des Lesekopfes, sondern auch noch in einigem Abstand davon erreicht wird, sodaß der Lesekopf in dieser Beziehung nicht empfindlich auf kleinere Abstandsänderungen von den Wiegand-Drähten reagiert.Thanks to the new type of reading head, the two permanent magnets, between which the E-shaped core lies, can be used to generate such a high field strength at a location in front of the working surface of the reading head, without the aid of a separate saturation magnet, that it is sufficient to pull Wiegand wires saturate (i.e. at least 80 A / cm), and to generate an oppositely directed magnetic field at a nearby location in front of the working surface of the reading head, the field strength of which is sufficient to magnetically reset a previously magnetically saturated Wiegand wire, ie reached at least 16 A / cm. These two places are passed through by the Wiegand wires during the reading process. The working surface of the reading head is understood to mean that surface to which the tips of the three legs of the E-shaped core lead and to which the Wiegand wires are guided during the reading process. The location at which the saturation field strength is reached and exceeded lies in front of the edges of the flux guide plates in the working surface of the reading head, which form strong local magnetic poles there, and so strong that the necessary saturation field strength is not only immediately in front of the working surface of the reading head, but also at some distance from it, so that the read head is not sensitive in this respect to small changes in distance from the Wiegand wires.

Der andere Ort, an welchem die Rückstellfeldstärke erreicht und überschritten wird, liegt im Streufeld der beiden nicht mit einem Flußleitblech belegten Polflächen der beiden Dauermagnete. Diese zwei nicht mit Flußleitblechen belegten Polflächen liegen hinter der Arbeitsfläche des Lesekopfes und in einigem Abstand vom oberen und unteren Schenkel des E-förmigen Kerns; da die Wiegand-Drähte bzw. der Lesekopf beim Lesevorgang so geführt werden, daß die Wiegand-Drähte mit ihren Enden jeweils vor zwei benachbarten Schenkeln des E-förmigen Kerns liegen (vergl. S. 6, Absatz 2), bedeutet dies, daß sie einerseits das starke lokale Magnetfeld vor den Flußleitblechen durchlaufen, aber andererseits zu den nicht mit Flußleitblechen belegten beiden Polflächen einen relativ großen Abstand aufweisen. Wegen dieses relativ großen Abstandes und weil das die magnetische Rückstellung bewirkende Magnetfeld von den relativ großen, nicht mit Flußleitblechen belegten Polflächen ausgeht, wird die nötige Rückstellfeldstärke in einem in Leserichtung relativ ausgedehnten Bereich erreicht und Änderungen des Abstandes der Wiegand-Drähte von der Arbeitsfläche sowie Verkippungen der Wiegand-Drähte relativ zur Leserichtung wirken sich deshalb weniger auf die Lesesicherheit aus als beim Stand der Technik, wo die Rückstellfeldstärke nur in einem in Leserichtung recht kurzen Bereich zwischen den entgegengesetzt gerichteten Magnetfeldern für die Sättigung und die Zündung der Wiegand-Drähte erreicht wird.The other place at which the reset field strength is reached and exceeded lies in the stray field of the two pole faces of the two permanent magnets not covered with a flux guide plate. These two pole faces not covered with flux guide plates lie behind the working surface of the reading head and at some distance from the upper and lower legs of the E-shaped core; Since the Wiegand wires or the reading head are guided during the reading process so that the ends of the Wiegand wires lie in front of two adjacent legs of the E-shaped core (see p. 6, paragraph 2), this means that they on the one hand pass through the strong local magnetic field in front of the flux guide plates, but on the other hand have a relatively large distance from the two pole faces not covered with flux guide plates. Because of this relatively large distance and because the magnetic field causing the magnetic recovery originates from the relatively large pole faces not covered with flux baffle plates, the necessary recovery field strength is achieved in a relatively extensive area in the reading direction and changes in the distance of the Wiegand wires from the working surface and tilting the Wiegand wires relative to the reading direction therefore have less of an effect on reading security than in the prior art, where the reset field strength is only achieved in a very short area in the reading direction between the opposing magnetic fields for the saturation and the ignition of the Wiegand wires.

Der erfindungsgemäße Lesekopf wird beim . Lesevorgang so geführt bzw. die Wiegand-Drähte werden beim Lesevorgang so geführt, daß sie als erstes das schwächere, für die magnetische Rückstellung der Wiegand-Drähte verantwortliche Magnetfeld durchqueren und danach die in der Arbeitsfläche des Lesekopfs liegenden Ränder der Flußleitstücke und das vonThe read head according to the invention is used. Reading process so guided or the Wiegand wires are guided during the reading process so that they first cross the weaker magnetic field responsible for the magnetic resetting of the Wiegand wires and then the edges of the flux guides in the working surface of the reading head and that of

ihnen ausgehende starke, die Sättigung der Wiegand-Drähte ermöglichende Magnetfeld passieren. Ein jeder Wiegand-Draht wird also zunächst magnetisch zurückgestellt, anschließend nach Passieren des Nulldurchgangs der magnetischen Feldstärke in dem nun entgegengesetzt gerichteten Magnetfeld mit steil ansteigender Feldstärke gezündet und weiter bis in den Bereich magnetischer Sättigung getrieben. Durch die auf das Zünden oder Triggern des Wiegand-Drahtes folgende Sättigung ist er für eine weitere magnetische Rückstellung und Zündung bereit. Sollte einmal ein Wiegand-Draht vor einer Rückstellung nicht hinreichend gesättigt gewesen sein oder einer unkontrollierten magnetischen Beeinflussung ausgesetzt gewesen sein, welche die Wirkung der vormaligen Sättigung zunichte gemacht hat, dann kann man das einfach dadurch beheben, daß man den Wiegand-Draht, nachdem er beim ersten Lesevorgang nicht korrekt gezündet hat, ein weiteres Mal am Lesekopf vorbeibewegt: nun wird er sicher zünden, da er beim ersten - nicht ordnungsgemäßen - Lesevorgang auf jeden Fall gesättigt wurde. Ausgefallene Wiegand-Impulse lassen sich innerhalb einer kodierten Impulsfolge durch eine Prüfschaltung ohne Schwierigkeiterkennen und wenn dieser Fall eintritt, kann die Prüfschaltung ein Signal abgeben, welches zur Wiederholung des Lesevorgangs auffordert.strong magnetic field that allows them to saturate the Wiegand wires. Each Wiegand wire is therefore initially magnetically reset, then ignited with a steeply increasing field strength after passing the zero crossing of the magnetic field strength in the now oppositely directed magnetic field and driven further into the area of magnetic saturation. As a result of the saturation following the ignition or triggering of the Wiegand wire, it is ready for a further magnetic reset and ignition. If a Wiegand wire has not been sufficiently saturated before a reset or has been exposed to an uncontrolled magnetic influence, which has nullified the effect of the previous saturation, you can fix it simply by changing the Wiegand wire after it did not ignite correctly during the first reading process, moved past the reading head again: now it will ignite safely, since it was saturated in any case during the first - incorrect - reading process. Failed Wiegand pulses can be recognized within a coded pulse sequence by a test circuit without difficulty and if this occurs, the test circuit can emit a signal which prompts the read process to be repeated.

Mit dem erfindungsgemäßen Aufbau für einen Lesekopf ist es gelungen, die Baulänge des Lesekopfes in Leserichtung um 10 mm bis 20 mm zu verkürzen und auch dann noch eine sichere Zündung der Wiegand-Drähte zu erreichen, wenn deren Abstand von der Arbeitsfläche bis auf 2 mm anwächst und/oder die Wiegand-Drähte um Winkel bis zu ± 15° um eine zu den Wiegand- Drähten parattete Achse verkippt am Lesekopf entlang geführt werden. Damit sind alle Voraussetzungen für eine erfolgreiche Anwendung in handgeführten Lesern gegeben. Beim Einsatz des Lesekopfes in stationären Kartenlesern hat die deutlich verkürzte Baulänge den Vorteil, daß die mit Wiegand-Drähten bestückten Karten entsprechend verkürzt werden können oder bei gleichbleibender Kartenlänge die Folge der Wiegand-Drähte entsprechend verlängert und damit der Informationsgehalt vergrößert werden kann.With the construction according to the invention for a reading head, it has been possible to shorten the overall length of the reading head in the reading direction by 10 mm to 20 mm and also to achieve a reliable ignition of the Wiegand wires when their distance from the working surface increases to 2 mm and / or the Wiegand wires are tilted by angles up to ± 15 ° about an axis paratted to the Wiegand wires along the reading head. This means that all the prerequisites for successful use in hand-held readers are met. When using the reading head in stationary card readers, the significantly shorter overall length has the advantage that the cards fitted with Wiegand wires can be shortened accordingly or, with the card length remaining the same, the sequence of Wiegand wires can be lengthened accordingly, thus increasing the information content.

Als Magnete eignen sich für die Erfindung wegen der mit ihnen erzielbaren'hohen magnetischen Kraftflüsse vor allem solche aus Legierungen Seltener Erden mit Kobalt, insbesondere aus Kobalt-Samarium.Suitable magnets for the invention are, owing to the high magnetic force fluxes that can be achieved with them, especially those made from rare earth alloys with cobalt, in particular from cobalt samarium.

Die Spitzen der Schenkel des E-förmigen Kerns befinden sich bei dem erfindungsgemäßen Lesekopf im Nahbereich der neutralen Zone des zwischen den Dauermagneten bestehenden Magnetfeldes (Unter dem Nahbereich der neutralen Zone wird jener Bereich um den räumlichen Nulldurchgang der Feldstärke verstanden, in welchem die magnetische Feldstärke noch wesentlich geringer ist als die zur Sättigung des weichmagnetischen Materials, aus welchem der E-förmige Kern besteht, erforderliche Feldstärke). Da die Zündung der Wiegand-Drähte bei verhältnismäßig niedriger Feldstärke nach ihrem Durchgang durch eben diese neutrale Zone erfolgt, also ebenfalls noch im Nahbereich der neutralen Zone und damit nahe bei den Enden der Schenkel des E-förmigen Kerns, ist gewährleistet, daß die beim Zünden des Wiegand-Drahtes auftretende sprunghafte Änderung eines magnetischen Kraftflusses unmittelbar den weichmagnetischen, E-förmigen Kern beeinflußt, welcher die Kraftflußänderung weiter in die elektrische Wicklung (Sensorwicklung) einkoppelt, welche sich auf dem mittleren Schenkel des E-förmigen Kerns befindet. Am besten ist die Einkopplung der beim Zünden eines Wiegand-Drahtes auftretenden Kraftflußänderung natürlich, wenn sich die Spitzen der Schenkel des E-förmigen Kerns genau an jenem Ort der Arbeitsfläche des Lesekopfes befinden, vor welchem die Wiegand-Drähte gezündet werden.The tips of the legs of the E-shaped core are located in the reading head according to the invention in the vicinity of the neutral zone of the magnetic field existing between the permanent magnets (the vicinity of the neutral zone is understood to mean the area around the spatial zero crossing of the field strength in which the magnetic field strength is still is substantially less than the field strength required to saturate the soft magnetic material from which the E-shaped core is made). Since the Wiegand wires are fired at a relatively low field strength after they have passed through this neutral zone, that is to say also in the vicinity of the neutral zone and thus close to the ends of the legs of the E-shaped core, this ensures that the firing occurs of the Wiegand wire sudden change in a magnetic force flow directly affects the soft magnetic, E-shaped core, which couples the change in force flow further into the electrical winding (sensor winding), which is located on the middle leg of the E-shaped core. The coupling of the change in force flow that occurs when a Wiegand wire is fired is, of course, best when the tips of the legs of the E-shaped core are located precisely at that location on the working surface of the reading head in front of which the Wiegand wire is fired.

Die in der Sensorwicklung erreichbare Impulsamplitude kann weiterhin dadurch wesentlich gesteigert werden, daß man durch eine Schrägstellung des E-förmigen Kerns im Lesekopf erreicht, daß dieser Kern sich nicht nur im Bereich der Arbeitsfläche des Lesekopfes, sondern insgesamt im Nahbereich der neutralen Zone des Magnetfeldes, also insgesamt im Einflußbereich einer möglichst geringen magnetischen Feldstärke befindet (Anspruch 3). Eine solche Anordnung ist vorteilhaft, weil sie eine Sättigung des E-förmigen Kerns durch das Magnetsystem vermeidet und somit die hohe Permeabilität des Kerns erhält. Beim Stand der Technik hingegen liegt der E-förmige Kern im Bereich starker Streufelder, welche ihn teilweise sättigen und dadurch weniger ansprechbar für weitere Kraftflußänderungen machen. Obendrein war es beim Stand der Technik nötig, den Kern wegen der Durchflutung durch zwei Magnetfelder mit entgegengesetzter Richtung durch eine nichtmagnetische Zwischenschicht zu unterteilen. Eine solche nicht-magnetische Zwischenschicht benötigt der Kern im erfindungsgemäßen Lesekopf nicht.The pulse amplitude that can be achieved in the sensor winding can be further increased significantly by an inclined position of the E-shaped core in the reading head, that this core is not only in the area of the working surface of the reading head, but overall in the vicinity of the neutral zone of the magnetic field, thus overall in the range of influence of the lowest possible magnetic field strength (claim 3). Such an arrangement is advantageous because it avoids saturation of the E-shaped core by the magnet system and thus maintains the high permeability of the core. In the prior art, however, the E-shaped core lies in the area of strong stray fields, which partially saturate it and thereby make it less responsive to further changes in the flow of force. On top of that, it was necessary in the prior art to subdivide the core due to the flow through two magnetic fields in the opposite direction by a non-magnetic intermediate layer. The core in the read head according to the invention does not require such a non-magnetic intermediate layer.

Grundsätzlich kann man durch entsprechende Formgebung der Flußleitbleche und des E-förmigen Kerns erreichen, daß die neutrale Zone des Magnetfelds den gesamten E-Kern durchzieht. Für die praktische Anwendung der Erfindung reicht es aber aus, die idealen Verhältnisse durch eine passende Orientierung und Zuordnung eines durch ebene Flächen begrenzten E-förmigen Kerns relativ zu den durch parallele, paarweise fluchtende Polflächen begrenzten und ebene Flußleitbleche tragenden Dauermagneten anzunähern, so wie das im Anspruch 3 angegeben ist. Die Verwendung ebenflächiger Bauteile erleichtert den Aufbau des Lesekopfes. Dabei werden die Magnete mit ihren Polflächen zweckmäßig - anders als beim Stand der Technik - im rechten Winkel zur Leserichtung orientiert, und der E-förmige Kern weist demgemäß einen von 90° verschiedenen Winkel zur Leserichtung auf. Die Leserichtung verläuft ihrerseits rechtwinklig zur Verbindungsgeraden der Spitzen der Schenkel des E-Kerns und parallel bzw. tangential zur Arbeitsfläche des Lesekopfes an dieser Stelle.Basically, by appropriate shaping of the flux guide plates and the E-shaped core, it can be achieved that the neutral zone of the magnetic field runs through the entire E-core. For the practical application of the invention, however, it is sufficient to approximate the ideal conditions by a suitable orientation and assignment of an E-shaped core delimited by flat surfaces relative to the permanent magnets delimited by parallel pole surfaces aligned in pairs and bearing flat flux guide plates, as in the Claim 3 is specified. The use of flat components simplifies the construction of the reading head. The magnets with their pole faces are expediently - at a right angle to - unlike in the prior art Reading direction oriented, and the E-shaped core accordingly has an angle of 90 ° to the reading direction. The reading direction is perpendicular to the straight line connecting the tips of the legs of the e-core and parallel or tangential to the working surface of the reading head at this point.

Ausführungsbeispiele der Erfindung sind schematisch in den beigefügten Zeichnungen dargestellt und werden nachfolgend beschrieben.

  • Figur 1 zeigt einen Lesekopf mit E-förmigem Kern in der Draufsicht auf die Arbeitsfläche,
  • Figur 2 zeigt den Schnitt 11-11 durch den Lesekopf aus Fig. 1,
  • Figur 3 zeigt die Seitenansicht 111 des Lesekopfes aus Fig. 1 und 2, und die
  • Figuren 4 - 6 sind Darstellungen entsprechend den Figuren 1 bis 3 eines Lesekopfes, welcher anstelle eines E-förmigen Kerns einen U-förmigen Kern aufweist.
Embodiments of the invention are shown schematically in the accompanying drawings and are described below.
  • FIG. 1 shows a read head with an E-shaped core in a top view of the work surface,
  • FIG. 2 shows the section 11-11 through the reading head from FIG. 1,
  • FIG. 3 shows the side view 111 of the reading head from FIGS. 1 and 2, and the
  • FIGS. 4-6 are representations corresponding to FIGS. 1 to 3 of a reading head which has a U-shaped core instead of an E-shaped core.

In den Ausführungsbeispielen sind gleiche oder einander entsprechende Teile mit übereinstimmenden Bezugszahlen bezeichnet.In the exemplary embodiments, identical or corresponding parts are identified by corresponding reference numbers.

Der in den Fig. 1 - 3 dargestellte Lesekopf enthält in einem nicht dargestellten Gehäuse einen weichmagnetischen, E-förmigen Kern 1, um dessen mittleren Schenkel 1c eine elektrische Wicklung 2 (Sensorwicklung) herumgelegt ist, sowie zwei plattenförmige, also kurze Dauermagnete 3 und 4 mit relativ großen Polflächen. Die ganze Anordnung aus Kern 1, Wicklung 2 und Magneten 3 ist in einen Kunststoff, insbes. in ein Gießharz eingebettet und dadurch lagemäßig fixiert. Aus Gründen der Übersichtlichkeit ist der Kunststoff selbst nicht dargestellt, jedoch ist in Fig. 2 und in Fig. 3 die Lage der Arbeitsfläche 6 des Lesekopfs angedeutet, welche durch die Oberfläche der Einbettmasse aus Kunststoff gebildet wird und in welcher die Spitzen 6a, 6b und 6c der drei Schenkel 1a, 1 b und 1 c des E-förmigen Kerns liegen.The reading head shown in FIGS. 1-3 contains a soft-magnetic, E-shaped core 1 in a housing (not shown), around whose central leg 1c an electrical winding 2 (sensor winding) is placed, and two plate-shaped, that is to say short, permanent magnets 3 and 4 with relatively large pole faces. The whole arrangement of core 1, winding 2 and magnet 3 is embedded in a plastic, in particular in a casting resin and thereby fixed in position. For reasons of clarity, the plastic itself is not shown, but the position of the working surface 6 of the reading head is indicated in FIG. 2 and in FIG. 3, which is formed by the surface of the plastic investment material and in which the tips 6a, 6b and 6c of the three legs 1a, 1b and 1c of the E-shaped core.

Die beiden Magnete 3 und 4 sind gleich groß, gleich stark und sind mit ihren Polflächen 3a und 3b bzw. 4a und 4b im rechten Winkel zur Leserichtung 7 angeordnet. Die Leserichtung 7 ist jene Richtung, in welche beim Lesevorgang der Lesekopf relativ zu den als ruhend angenommenen Wiegand-Drähten 8 und 9 geführt wird. Im rechten Winkel zur Leserichtung sind auch die Verbindungsgeraden der Spitzen 6a, 6b und 6c der drei Schenkel des E-förmigen Kerns 1 angeordnet; wie man jedoch am besten an Hand der Fig. 2 erkennen kann, weist der E-Kern als ganzes keinen rechten Winkel mit der Leserichtung 7 auf, d.h., die beiden Ebenen, in welchen die beiden Seitenflächen des E-förmigen Kerns 1 liegen, weisen einen von 90° verschiedenen Winkel mit der Leserichtung 7 auf. Die Spitzen 6a, 6b und 6c der drei Schenkel des E-förmigen Kerns 1 sind jedoch derart abgeschrägt, daß sie in der Flucht der Arbeitsfläche 5 liegen.The two magnets 3 and 4 are the same size, the same strength and are arranged with their pole faces 3a and 3b or 4a and 4b at right angles to the reading direction 7. The reading direction 7 is the direction in which the reading head is guided relative to the Wiegand wires 8 and 9, which are assumed to be at rest, during the reading process. The connecting straight lines of the tips 6a, 6b and 6c of the three legs of the E-shaped core 1 are also arranged at right angles to the reading direction; However, as can best be seen from FIG. 2, the E core as a whole does not have a right angle with the reading direction 7, that is to say the two planes in which the two side faces of the E-shaped core 1 lie an angle other than 90 ° with the reading direction 7. However, the tips 6a, 6b and 6c of the three legs of the E-shaped core 1 are chamfered in such a way that they lie in alignment with the work surface 5.

Die beiden Dauermagnete 3 und 4 sind in einigem Abstand unter der Arbeitsfläche 5 sowie - in Richtung quer zur Leserichtung 7 gemessen - in einigem Abstand von den Schenkeln 1a und 1 b des E-förmigen Kerns 1 angeordnet. Die Anordnung ist so getroffen, daß in Blickrichtung parallel zur Arbeitsfläche 5, aber quer zur Leserichtung 7 die drei Schenkel 1a - 1c des E-förmigen Kerns 1 die beiden Magnete 3 und 4 ungefähr diagonal kreuzen (siehe Fig. 2).The two permanent magnets 3 and 4 are arranged at some distance below the work surface 5 and - measured in the direction transverse to the reading direction 7 - at some distance from the legs 1a and 1b of the E-shaped core 1. The arrangement is such that the three legs 1a - 1c of the E-shaped core 1 cross the two magnets 3 and 4 approximately diagonally parallel to the working surface 5, but transversely to the reading direction 7 (see FIG. 2).

Die beiden Magnete 3 und 4 sind relativ zueinander antiparallel orientiert, und beide tragen auf einer ihrer Polflächen 3a bzw. 4b je ein Flußleitblech 13 bzw. 14. Die Flußleitbleche befinden sich auf ungleichnamigen Polflächen 3a bzw. 4b der beiden Magnete und fluchten miteinander. Die ebenen Flußleitbleche 13 und 14 bedecken die jeweiligen Polflächen 3a bzw. 4b vollständig und führen won dem der Arbeitfläche 5 nächstliegenden Rand der Magnete 3 bzw. 4 bis zur Arbeitsfläche 5 des Lesekopfes und nähern sich dabei - in der Draufsicht auf die Arbeitsfläche gesehen, siehe Fig. 1 - den beiden äußeren Schenkeln 1 und 1 b des E-förmigen Kerns bis auf einen geringen Abstand an. In Leserichtung 7 gemessen bleibt jedoch trotz dieser Annäherung zwischen den in der Arbeitsfläche 5 liegenden Enden der Flußleitbleche 13 und 14 und den Spitzen 6a und 6b des E-förmigen Kerns 1 ein beträchtlicher Abstand erhalten (siehe Fig. 2).The two magnets 3 and 4 are oriented antiparallel relative to each other, and both carry a flux guide plate 13 or 14 on one of their pole faces 3a or 4b. The flat flux guide plates 13 and 14 completely cover the respective pole surfaces 3a and 4b and lead to the edge of the magnets 3 and 4 closest to the working surface 5 to the working surface 5 of the reading head and, as seen in the plan view of the working surface, approach each other, see Fig. 1 - the two outer legs 1 and 1 b of the E-shaped core to a short distance. Measured in the reading direction 7, however, despite this approach, a considerable distance remains between the ends of the flow guide plates 13 and 14 lying in the working surface 5 and the tips 6a and 6b of the E-shaped core 1 (see FIG. 2).

Die elektrische Wicklung 2 ist mit ihrer Längsachse im gezeichneten Beispiel senkrecht zur Arbeitsfläche 5 orientiert und schließt deshalb einen von 0 verschiedenen Winkel mit dem mittleren Schenkel 1c des E-förmigen Kerns ein, jedoch ist eine derartige Orientierung der Wicklung 2 nicht zwingend. Die Orientierung der elektrischen Wicklung 2 ist nicht erfindungswesentlich, sie könnte auch anders gewählt sein.The electrical winding 2 is oriented with its longitudinal axis perpendicular to the working surface 5 in the example shown and therefore includes an angle different from 0 with the central leg 1c of the E-shaped core, but such an orientation of the winding 2 is not mandatory. The orientation of the electrical winding 2 is not essential to the invention, it could also be chosen differently.

Der in den Fig. 1 bis 3 dargestellte Lesekopf dient zum Lesen einer Information, welche in zwei Zeilen von Wiegand-Drähten kodiert ist, von denen je ein Wiegand-Draht 8 bzw. 9 beispielsweise dargestellt ist. Die Länge der Wiegand-Drähte 8 und 9 und die Lage der Spitzen 6a, 6b und 6c des E-förmigen Kerns 1 sind so aufeinander abgestimmt, dass die Wiegand-Drähte 8 der einen Zeile mit ihren Enden über die Spitzen 6a und 6c und die Wiegand-Drähte 9 der anderen Zeile mit ihren Enden über die Spitzen 6c und 6b des E-förmigen Kerns 1 bewegt werden, wenn der Lesekopf in Leserichtung quer zu den Wiegand-Drähten 8 und 9 längs den Wiegand-Drahtteilen geführt wird.The reading head shown in FIGS. 1 to 3 is used to read information which is coded in two rows of Wiegand wires, of which one Wiegand wire 8 or 9 is shown, for example. The length of the Wiegand wires 8 and 9 and the position of the tips 6a, 6b and 6c of the E-shaped core 1 are coordinated with one another such that the Wiegand wires 8 of the one line have their ends over the tips 6a and 6c and Wiegand wires 9 of the other line are moved with their ends over the tips 6c and 6b of the E-shaped core 1 when the read head is guided in the reading direction transverse to the Wiegand wires 8 and 9 along the Wiegand wire parts.

Ein zuvor magnetisch gesättigter Wiegand-Draht gelangt beim Lesevorgang zunächst in das relativ weit ausgreifende Magnetfeld, welches zwischen den beiden Polflächen 3b und 4a aufgespannt ist und wird durch dieses magnetisch zurückgestellt. Im Bereich der Spitzen 6a und 6c bzw. 6b und 6c des E-förmigen Kerns 1 durchquert der Wiegand-Draht 8 bzw. 9 einen räumlichen Nulldurchgang der Feldstärke und gelangt dann in den Bereich des Magnetfeldes, welches zwischen den Polflächen 3a und 4b, welche mit den Flußleitblechen 13 und 14 belegt sind, aufgespannt ist und jenseits des räumlichen Nulldurchgangs der Feldstärke steil ansteigt. Kurz nach dem Passieren des Nulldurchgangs der Feldstärke wird der Wiegand-Draht 8 bzw. 9 gezündet und wird bis in die magnetische Sättigung getrieben, wenn er in den Bereich der Flußleitbleche 13 und 14 gelangt, zwischen denen ein starkes lokales Magnetfeld besteht. Durch diese dem Zünden folgende Sättigung ist der Wiegand-Draht 8 bzw. 9 sofort für einen weiteren Lesevorgang bereit.During the reading process, a previously magnetically saturated Wiegand wire first reaches the relatively extensive magnetic field that is spanned between the two pole faces 3b and 4a and is magnetically reset by this. In the region of the tips 6a and 6c or 6b and 6c of the E-shaped core 1, the Wiegand wire 8 or 9 crosses a spatial zero crossing of the field strength and then reaches the area of the magnetic field, which is spanned between the pole faces 3a and 4b, which are covered with the flux guide plates 13 and 14, and which rises steeply beyond the spatial zero crossing of the field strength. Shortly after passing the zero crossing of the field strength, the Wiegand wire 8 or 9 is ignited and is driven to magnetic saturation when it reaches the area of the flux guide plates 13 and 14, between which there is a strong local magnetic field. As a result of this saturation following ignition, the Wiegand wire 8 or 9 is immediately ready for another reading process.

Die beim Zünden des Wiegand-Drahtes auftretende plötzliche Änderung des magnetischen Kraftflusses bewirkt eine ebenso plötzliche Änderung des Magnetisierungszustandes des E-förmigen Kerns 1, und dieses führt in der Wicklung 2 zu einem elektrischen Impuls, dessen Polarität davon abhängt, ob der Wiegand-Draht, der gerade gezündet wurde, an den Schenkeln 1a und 1c c oder an den Schenkeln 1b und 1c entlang bewegt wurde..The sudden change in the magnetic force flow that occurs when the Wiegand wire is ignited causes an equally sudden change in the magnetization state of the E-shaped core 1, and this leads to an electrical pulse in the winding 2, the polarity of which depends on whether the Wiegand wire, which was just ignited, was moved along the legs 1a and 1c c or along the legs 1b and 1c ..

Infolge der Schrägstellung des E-förmigen Kerns relativ zu den beiden Dauermagneten 3 und 4 und durch die gewählte besondere Anordnung der Flußleitbleche 13 und 14 ist es gelungen, den E-förmigen Kern 1 insgesamt in einem Bereich mit relativ geringer magnetischer Feldstärke anzuordnen. Dies hat den Vorteil, daß die beim Zünden der Wiegand-Drähte auftretenden Änderungen des magnetischen Kraftflusses in einen weitgehend ungesättigten Kern eingekoppelt werden und deshalb zu hohen Signalamplituden führen.As a result of the inclined position of the E-shaped core relative to the two permanent magnets 3 and 4 and due to the chosen special arrangement of the flux guide plates 13 and 14, it has been possible to arrange the E-shaped core 1 overall in a region with a relatively low magnetic field strength. This has the advantage that the changes in the magnetic force flow that occur when the Wiegand wires are ignited are coupled into a largely unsaturated core and therefore lead to high signal amplitudes.

Das in den Fig. 4 bis 6 dargestellte Ausführungsbeispiel unterscheidet sich von jenem in den Fig. bis 3 nur darin, daß statt eines E-förmigen Kernes 1 ein U-förmiger Kern 11 Verwendung gefunden hat, welcher auf seinem Joch 12 die erforderliche elektrische Wicklung 2 trägt. Ein solcher Lesekopf dient zum Lesen der Information, welche in einer einzelnen Zeile von Wiegand-Drähten 8 enthalten ist. Der Abstand der beiden Schenkel 11 a und 11b des U-förmigen Kerns 11, dessen Spitzen 16a und 17a wiederum in der Arbeitsfläche 6 des Lesekopfes liegen, ist so auf die Länge der Wiegand-Drähte 8 abgestimmt, daß die Enden der Wiegand-Drähte beim Lesevorgang, wenn der Lesekopf im rechten Winkel zu den Wiegand-Drähten geführt wird, an den Spitzen 16a und 16b des Kerns 11 vorbeigefÜhrt werden.The embodiment shown in FIGS. 4 to 6 differs from that in FIGS. To 3 only in that instead of an E-shaped core 1, a U-shaped core 11 has been used, which has the required electrical winding on its yoke 12 2 wears. Such a reading head is used to read the information contained in a single line of Wiegand wires 8. The distance between the two legs 11 a and 11 b of the U-shaped core 11, the tips 16 a and 17 a are in turn in the working surface 6 of the reading head, is matched to the length of the Wiegand wires 8 that the ends of the Wiegand wires at Reading operation, when the reading head is guided at right angles to the Wiegand wires, be guided past the tips 16a and 16b of the core 11.

Bei einem solchen Lesekopf treten nur Impulse einer Polarität auf. Im übrigen entsprechen die Verhältnisse jenen im Beispiel der Fig. 1 bis 3.With such a read head, only pulses of one polarity occur. Otherwise, the conditions correspond to those in the example in FIGS. 1 to 3.

Claims (5)

1. A reading head for magnetically scanning two rows of juxtaposed parallel Wiegand wires or the like elongate bistable magnetic elements,
which reading head comprises a soft magnetic E-shaped core consisting of three parallel legs, which have tips terminating on the working surface of the reading head and are interconnected at their other end by a yoke, which is disposed behind the working surface of the reading head, wherein the intermediate leg is surrounded by an electric winding (sensor winding).
which reading head comprises behind its working surface an arrangement consisting of two short permanent magnets, which have the same strength and relatively large pole faces and one of which is spaced above the upper leg of the E and theother is spaced below the lower leg of the E and both of which have a magnetization in a direction which is approximately parallel to the working surface,
wherein the arrangement of the permanent magnets is such that that magnetic field existing between the permanent magnets has a flux component that is parallel to the direction of the yoke of the E-shaped core and said flux component on one side of the E-shaped core is directed opposite to said flux component on the other side of the E-shaped core,
characterized in that respective flux-conducting sheets (13, 14) are carried by one permanent magnet (3) on its north pole face (3a) and by the other permanent magnet (4) on its south pole face (4b),
that the distance between the flux-conducting sheets (13, 14), measured parallel to the yoke (12) decreases to a value which is approximately as large as the height of the E-shaped core as they extend as far as to the working surface (5) of the reading head and that the tips (6a, 6b, 6c) of the legs (1a, 1b, 1c) of the E-shaped core (1) are disposed in said working surface (5) at such a distance from the flux-conducting sheets (13, 14) that said tips are disposed in the rear range of the neutral zone (15) of the magnetic field.
2. A reading head for magnetically scanning two rows of juxtaposed parallel Wiegand wires or the like elongate bistable magnetic elements,
which reading head comprises a soft magnetic U-shaped core consisting of two parallel legs, which have tips terminating on the working surface of the reading head and are interconnected at their other end by a yoke, which is disposed behind the working surface of the reading head and is surrounded by an electric winding (sensor winding),
which reading head comprises behind its working surface an arrangement consisting of two short permanent magnets, which have the same strength and relatively large pole faces and one of which is spaced above the upper leg of U and the other of which is spaced below the lower leg of the U and both of which have a magnetization in a direction which is approximately parallel to the working surface,
wherein the arrangement of the permanent magnets is such that that magnetic field existing between the permanent magnets has a flux component that is parallel to the direction of the yoke of the U-shaped core and said flux component on one side of the U-shaped core is directed opposite to said flux component on the other side of the U-shaped core,
that the distance between the flux-conducting sheets (13, 14), measured parallel to the yoke (12). decreases to a value which is approximately as large as the height of the U-shaped core as they extend as far as to the working surface (5) of the reading head and that the tips (16a, 16b) of the legs (11 a, 11 b) of the U-shaped core (11) are disposed in said working surface at such a distance from the flux-conducting sheets (13, 14) that said tips (16a, 16b) are disposed in the near range of the neutral zone (15) of the magnetic field.
3. A reading head according to claim 1 or 2, characterized in that the E-shaped or U-shaped core (1, 11) is so arranged relative to the two permanent magnets (3, 4) and their flux-conducting sheets (13, 14) that said core is entirely disposed in the near range of the neutral zone (15) of the magnetic field.
4. A reading head according to claim 3, characterized in that the planar pole faces (3a, 3b; 4a, 4b) of the platelike permanent magnets (3, 4) are aligned in pairs and said pole faces as well as the planar flux-conducting sheets (13, 14) of said magnets include with the E-shaped or U-shaped core (1, 11) an angle which differs from zero degree and the yoke (12) of the E-shaped or U-shaped core is approximately aligned with those pole faces (3a, 4b) which are covered by the flux-conducting sheets (13, 14).
5. A reading head according to any of the preceding claims, characterized in that the planar pole faces (3a, 3b; 4a, 4b) of the permanent magnets (3, 4) extend at right angles to the reading direction.
EP84111893A 1983-11-10 1984-10-04 Read head for magnetically sensing wiegand wires Expired EP0144601B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3340600A DE3340600C1 (en) 1983-11-10 1983-11-10 Read head for magnetic scanning of Wiegand wires
DE3340600 1983-11-10

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EP0144601A1 EP0144601A1 (en) 1985-06-19
EP0144601B1 true EP0144601B1 (en) 1987-06-10

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EP (1) EP0144601B1 (en)
DE (1) DE3340600C1 (en)

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US4944270A (en) * 1987-03-31 1990-07-31 Akira Matsushita Asymmetrical excitation type magnetic device and method of manufacture thereof
US4758742A (en) * 1987-04-14 1988-07-19 Echlin Inc. Shunt activated pulse generator
DE3741780A1 (en) * 1987-12-10 1989-06-29 Karl Harms Handels Gmbh & Co K MAGNETIC THEFT OR BURGLAR SECURITY SYSTEM AND SENSOR METAL ELEMENT SUITABLE FOR THIS
JP2563597B2 (en) * 1989-08-04 1996-12-11 松下電器産業株式会社 Composite thin film magnetic head
KR940004989B1 (en) * 1989-08-04 1994-06-09 마쯔시다덴기산교 가부시기가이샤 Thin film magnetic head
US5817207A (en) 1995-10-17 1998-10-06 Leighton; Keith R. Radio frequency identification card and hot lamination process for the manufacture of radio frequency identification cards
ES2196372T3 (en) * 1996-10-09 2003-12-16 Flying Null Ltd MAGNETIC INTERROGATION TECHNIQUES.
GB9919100D0 (en) * 1999-08-12 1999-10-13 Sentec Ltd Improved tag readers

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EP0144601A1 (en) 1985-06-19
US4635227A (en) 1987-01-06
DE3340600C1 (en) 1985-01-10

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